Mediocre sales people are content to react to the requests of their customers, and focus on maintaining the relationships in order to solidify the business they enjoy.
The best sales people understand that, while some of the above is necessary, they proactively seek to discover additional opportunities for growth in their key accounts and strategically build relationships with people who can open doors for them.
The difference is greater than just one of degree. The best sales people work from a mindset that understands they need to continually seek for additional opportunities. This mindset colors everything they do, and dictates the practices and disciplines they build into their routines.